The Federal Communications Commission proposal to open up a big swath of new spectrum for Wi-Fi is encountering opposition from an unlikely source: the auto industry. Carmakers aren’t against the idea of more unlicensed airwaves, but they are concerned that devices using those frequencies would interfere with the talking car networks they want to launch in the next few years.

Last month at CES, FCC Chairman Julius Genachowski announced that the commission was moving forward with a plan to clear 195 MHz of spectrum in the 5 GHz band for Wi-Fi use. Those new frequencies, however, abut the 5.9 GHz airwaves the government has set aside for future vehicle-to-vehicle communications networks.

On Monday, the Intelligent Transportation Society of America (ITSA) sent a letter to the FCC — signed by a veritable who’s who in the transportation industry such as AAA, Chrysler, Mercedes-Benz and Hyundai — warning the FCC of the potential for these new Wi-Fi networks to interfere with the wireless transmissions between connected cars.

“We support efforts to identify spectrum that may be utilized to expand Wi-Fi applications,” ISTA said in a statement. “But with over 30,000 deaths on our nation’s roads every year, we also believe it is critical that efforts to open up additional spectrum do not come at the expense of revolutionary life-saving technologies.”

If the commercial Wi-Fi signals were to bleed out into the protected Wi-Fi signals of the car network, the letter said, the public safety and transportation management benefits of the network could be nullified — along with the hundreds of millions of dollars automakers and the government have invested in developing the technology. The auto industry doesn’t want the FCC’s Wi-Fi plan stopped, but it did ask regulators to guarantee that safeguards would be in place ensuring that such interference doesn’t occur.

That might be easier said then done. Interference issues have killed more than one big spectrum proposal as LightSquared can attest. In this case, the cars and the Wi-Fi devices would be using short-range wireless technologies, which might help mitigate interference issues. But as anyone who has ever turned on their smartphone’s Wi-Fi radio in a car knows, you can pick up a Wi-Fi signal almost anywhere. And as outdoor Wi-Fi deployments become more prevalent, those signals are only going to get more powerful.